Itain't necessarily so!
There was so much garbage written in this article, that it's apparent that the writer has no idea how (or why) a diesel engine works. The diesel engine and the petrol engine work by two entirely different concepts . That for the petrol engine is combustion at constant volume, that of the diesel combustion at constant pressure. In the petrol engine the fuel and air are compressed until ignited by the spark. The gas/air mixture burns in a flash. The pressure rises instantly and provides the driving force. In the diesel, the air alone is compressed . At the end of compression, the fuel is sprayed in over a period of time, so the pressure remains the same, since the piston is descending on the power stroke. The Pressure/Volume (PV) diagram for the diesel is nearer the ideal (The Carnot Cycle, which indicates the ultimate efficiency that may be obtained) than that of the petrol. In practise, the distinction is slightly blurred, but the distinction is still appropriate. Oddly the diesel as invented by Herr Diesel is not a diesel engine in that it is not combustion at constant volume, but, like the petrol engine is combustion at constant volume. In fact the only diesel engines still in use are the engines made for model aircraft, and as far as I know the last commercial true diesel engine was the Vincent Firefly, a cycle motor made in the mid fifties by the Vincent Motorcycle Company during the craze for motor assisted bicycles. It should be noted that Herr Diesel was NOT the inventor of the Diesel Engine that bears his name. The true diesel engine was invented by gentleman of the name Ackroyd-Stuart. His engine was being made and sold by Hornsby and Company of Lincoln, two years before Herr Diesel built his engine. It is this engine on which the modern diesel is based.
In this debacle, my sympathies lie entirely with Volks Wagen and other car manufactures. . Governments issue directives. The directives do not have to based on logic, or indeed have to be obtainable under the laws of Thermodynamics. No doubt the car manufactures argued long and hard to convince the authorities otherwise/ To no avail I've a sneaking suspicion that VW have done nothing unlawful. No doubt their lawyers and engineers have long laboured to create a test which adheres tightly to the provisions of the statute. Much like Google, Apple, Starbucks, etc have laboured long to establish a financial regime which avoids paying taxes, entirely within the legal requirements. The article writer did make one point which seems to have been missed by most other commentators. The US has no diesel powered car manufacture. Every diesel powered car imported to the US is one car not manufactured by the US car industry. I'm sure that their lawyers and engineers laboured long and hard to formulate rules which would effectively exclude the VW from the US